What is the clinical presentation of a single large vesicle due to Herpes Simplex Virus (HSV) in a person of African descent?

Clinical Presentation of Single Large HSV Vesicle in Persons with Darker Skin

A single large vesicle due to Herpes Simplex Virus (HSV) in a person with darker skin typically appears as a fluid-filled blister that may be less visibly erythematous at the base compared to lighter skin tones, but still presents with the characteristic progression from papule to vesicle to ulcer to crust.

Characteristic Appearance

HSV lesions in darker skin follow the same pathophysiological progression as in lighter skin, but with some important visual differences:

• Initial Presentation:

  • Begins as a papule that rapidly evolves to a vesicle
  • May be preceded by a sensory prodrome (pain, tingling, or pruritis) in the affected area 1
  • The erythema (redness) at the base may be more subtle or appear as darkening rather than reddening 2

• Vesicle Stage:

  • Clear, fluid-filled blister containing thousands of infectious viral particles 1
  • In a single large vesicle presentation, the lesion is typically tense and dome-shaped
  • May appear more hyperpigmented at the base rather than erythematous 2

• Evolution:

  • Progresses to shallow ulceration after the vesicle ruptures 1
  • Forms crusts during healing 1
  • Typically heals without scarring unless secondary bacterial infection occurs 1, 2

Location and Distribution

The location of HSV lesions depends on the type and mode of transmission:

• HSV-1: Commonly affects the orolabial region (lips, mouth, chin) 2
• HSV-2: Typically affects genital areas, buttocks, thighs, or perineum 1
• Both types: Can appear on any skin surface through autoinoculation

Diagnostic Considerations

Visual diagnosis of HSV in darker skin can be challenging due to:

1. Less obvious erythema at the base of lesions
2. Potential for post-inflammatory hyperpigmentation during healing
3. Atypical presentations, especially in immunocompromised individuals 1

Laboratory confirmation is strongly recommended:

• PCR testing: Most sensitive method (approaching 100% sensitivity) 2
• Viral culture: Alternative when PCR unavailable 2
• Direct immunofluorescence: Can differentiate HSV from VZV 2
• Type-specific serology: Useful for determining HSV-1 vs HSV-2 1

Special Considerations in Immunocompromised Patients

In immunocompromised individuals:

• Lesions may be larger, deeper, and more persistent 1
• Multiple lesions may coalesce into a larger ulcerated area 1
• Healing is typically slower and may require antiviral therapy 1
• Atypical presentations are more common 2
• Risk of disseminated infection is higher 1

Differential Diagnosis

A single large vesicle could be confused with:

• Varicella zoster virus (shingles) - typically multiple vesicles in a dermatomal distribution 1
• Contact dermatitis with vesicular reaction 3
• Fixed drug eruption 3
• Bullous impetigo or other bacterial infections
• Autoimmune bullous disorders

Clinical Pearls

1. Always obtain laboratory confirmation for suspected HSV lesions, especially in darker skin where visual diagnosis may be more challenging 1

2. Sample collection should be done from active lesions, preferably vesicles, as timing matters in diagnosis 2

3. Typing of the virus (HSV-1 vs HSV-2) is important as HSV-1 recurs less frequently than HSV-2 in the genital area 1

4. In darker skin, post-inflammatory hyperpigmentation may persist after the lesion has healed

5. Treatment with antiviral medications (acyclovir, valacyclovir, famciclovir) can accelerate healing and reduce viral shedding 4

By understanding the unique presentation of HSV lesions in darker skin, clinicians can improve diagnostic accuracy and provide appropriate treatment to reduce symptoms and prevent transmission.